Once the initial shock wore off, it appeared that Gearbox are primarily interested in updating the existing games for re-release on modern PCs (and possibly other formats). Whilst the money spent indicates they will be pursuing a fourth game in the series, they have also indicated a willingness to talk to other companies about it. There is some hope that they might talk to Blackbird Interactive, where quite a few of the original Homeworld developers ended up to work on a new strategy game called Hardware. Another company, Team Pixel, had also put a lot of work into a possible iOS-based version of the game, which I imagine Gearbox would be very interested in.
Confusingly, the purchase only includes the rights to Homeworld and Homeworld 2. The fate of the rights to Homeworld: Cataclysm (the best of the three games in the series) seems to be unknown at present.
Update: The original Homeworld creators at Blackbird have congratulated Gearbox and released some unseen concept art about the game. Blackbird also indicated they would be open to talking to Gearbox about any future project. Gearbox outsourcing a Homeworld 3 to Blackbird (the same way that Bethesda outsourced Fallout: New Vegas to Obsidian, where most of the original Fallout creators had ended up) would be a very smart move indeed.